This, I think, is the place to suggest that a proposal which I previously put forward as a provisional assumption should be taken in earnest. In the latest analytical literature[32] a predilection has been shown for the view that any kind of privation, any thwarted instinctual gratification, results in a heightening of the sense of guilt, or may do so. I believe one obtains a great simplification of theory if one regards this as valid _only_ for the aggressive instincts, and that little will be found to contradict this assumption. How then is it to be explained dynamically and economically that a heightening of the sense of guilt should appear in place of an unfulfilled erotic desire? This can surely only happen in a roundabout way: the thwarting of the erotic gratification provokes an access of aggressiveness against the person who interfered with the gratification, and then this tendency to aggression in its turn has itself to be suppressed. So then it is, after all, only the aggression which is changed into guilt, by being suppressed and made over to the super-ego. I am convinced that very many processes will admit of much simpler and clearer explanation if we restrict the findings of psycho-analysis in respect of the origin of the sense of guilt to the aggressive instincts. Reference to the clinical material here gives us no unequivocal answer, because, according to our own hypothesis, the two kinds of instincts hardly ever appear in a pure form, unmixed with each other; but the investigation of extreme cases would probably point in the direction I anticipate. I am tempted to extract our first advantage from this narrower conception by applying it to the repression-process. The symptoms of neurosis, as we have learnt, are essentially substitutive gratifications for unfulfilled sexual wishes. In the course of our analytic work we have found to our surprise that perhaps every neurosis masks a certain amount of unconscious sense of guilt, which in its turn reinforces the symptoms by exploiting them as punishment. One is now inclined to suggest the following statement as a possible formulation: when an instinctual trend undergoes repression, its libidinal elements are transformed into symptoms and its aggressive components into a sense of guilt. Even if this statement is only accurate as an approximation it merits our interest.